Field of the Invention
The invention relates to a press-fit type connector terminal to be inserted into an electrically conductive through-hole formed through a printed circuit board.
Description of the Related Art
Various press-fit type connector terminals have been suggested. For instance, they have a terminal contact section having a cross-section in a needle-eye, C-shaped, N-shaped or Σ-shaped form.
Japanese Patent Application Publication No. 2004-134275 has suggested a connection terminal including a head to which a cable is connected, and a body to be inserted into a through-hole formed through a substrate. The body is centrally formed with a hole extending in a length-wise direction thereof, and the hole is formed with a plurality of slits extending from an inner wall to an outer wall of the body. The hole is filled with electrically conductive adhesive.
Japanese Patent Application Publication No. 2007-157469 has suggested a press-fit type terminal including a press-fit section, a terminal base, and a male terminal. The press-fit section includes a contact having a shape which is readily able to make contact with a through-hole, and a compression section composed of elastic material. The compression section is inserted into an opening of the contact, and the compression section exerts an elastic force on the contact such that the contact is compressed onto the through-hole.
The International Publication WO 2006/077827 has suggested a press-fit terminal including a press-fit contact section making electrical contact with an electrically conductive through-hole formed through a printed circuit board. A single underlying plating layer or a plurality of underlying plating layer is(are) formed on a surface of a base material of the press-fit contact section. On the uppermost playing layer is formed a layer composed of an alloy of Sn and a plating metal of which the uppermost playing layer is composed, and non-alloyed Sn is mixed in an outermost layer of the alloy layer.
Since the above-identified conventional press-fit type connector terminals are designed to have an outer diameter greater than an inner diameter of a through-hole formed through a printed circuit board, and have a press-fit section having low elasticity and to be inserted into a through-hole for making contact with the through-hole, a printed circuit board tends to be whitened due to a contact pressure exerted on the through-hole by the press-fit section, and a playing layer of the through-hole sometimes peels off. Since whitening of a printed circuit board means molecular destruction of components of which the board is composed, the molecular destruction induces not only degradation in electrical insulation of a printed circuit board and deterioration in a withstand voltage, but also an increase in a resistance of a circuit pattern.